I have already told you that the tenth Amendment clearly makes secession illegal based upon the fact that it sepcifically states states rights to be those NOT delegated to the United State through the Constitution.
The States had no right then to usurp the rights delegated to the US if you believe in the 10th Amendment, which obviously you dont.
You can pick any power delegated in the Constitution to the United States and the tenth Amendment clearly states it as NOT a state right.
The Confederacy committed treason to try to usurp even the smallest power to the greatest power from the Union. The tenth clearly stated that they had NOT that power.